a. Field of the Invention
The present invention relates to data storage systems of the type that include a housing having an opening for receipt of a removable disk cartridge in which an information recording medium is mounted for protection. More particularly, it relates to a cartridge loading apparatus for loading a removable disk cartridge onto and for unloading a removable disk cartridge from a magnetically clamped spindle interface for rotation relative to a read-write head.
b. Background Art
The demand for mass data storage continues to increase with expanding use of data processing systems and personal computers. Optical data storage systems are becoming an increasingly popular means for meeting this expanding demand. These optical data systems provide large volumes of relatively low-cost storage that may be quickly accessed.
In optical disk systems, coded video signals, audio signals, or other information signals are recorded on a disk in the form of information tracks on one or both planar surfaces of the disk. At the heart of an optical storage system is at least one laser (or other light source). In a first operating mode, the laser generates a high-intensity laser beam that is focused on a small spot on an information track of a rotating storage disk. This high-intensity laser beam raises the temperature of the recording surface of the material above its Curie Point--the point at which the material loses its magnetization and accepts the magnetization of the magnetic field in which the disk is placed. Thus, by controlling or biasing this surrounding magnetic field, and allowing the disk to cool below its Curie Point in a controlled magnetic environment, information may be recorded on the disk in the form of "pits" or "marks" on the recording medium.
Subsequently, when the operator desires to reproduce or read the previously recorded information, the laser enters a second operating mode. In this mode, the laser generates a low-intensity laser beam that is again focused on the tracks of the rotating disk. This lower intensity laser beam does not heat the disk above its Curie Point. The laser beam is, however, reflected from the disk surface in a manner indicative of the previously recorded information due to the presence of the previously formed pits or marks, and the previously recorded information may thereby be reproduced. Since the laser may be tightly focused, an information processing system of this type has advantages of high recording density and accurate reproduction of the recorded information.
The components of a typical optical system include a housing with an insertion port through which the user inserts the recording media into the drive. This housing accommodates, among other items, the mechanical and electrical subsystems for loading, reading from, writing to, and unloading an optical disk. The operation of these mechanical and electrical subsystems are typically within the exclusive control of the data processing system to which the drive is connected.
Within the housing of a conventional system that uses disk cartridges, a turntable for rotating a disk thereon is typically mounted on the system baseplate. The turntable may comprise a spindle having a magnet upon which a disk hub is mounted for use. The magnet attracts the disk hub, thereby holding the disk in a desired position for rotation.
In optical disk systems, as discussed above, it is necessary to magnetically bias the disk during a writing operation by applying a desired magnetic field to at least the portion of the disk being heated by the laser during the writing (recording or erasing) operation. Thus, it is necessary to mount a magnetic field biasing device where it may be conveniently placed in close proximity to the disk surface when the disk is held in position by the magnet associated with the spindle.
A variety of media or disk types are used in optical data storage systems for storing digital information. For example, standard optical disk systems may use 51/4 inch disks, and these optical disks may or may not be mounted in a protective case or cartridge. If the optical disk is not fixedly mounted in a protective cartridge, an operator manually removes the disk from the protective case. The operator would then manually load the disk onto a loading mechanism, using care to prevent damage to the recording surface.
Alternatively, for purposes of convenience and protection, a disk may be mounted within an enclosure or a cartridge that is itself inserted into the insertion port of the drive and is then conveyed to a predetermined position. These disk cartridges are well known in the computer arts. The disk cartridge comprises a cartridge housing containing a disk upon which data may be recorded.
To protect the disk when the cartridge is external from the drive, the disk cartridge typically includes at least one door or shutter that is normally closed. The cartridge shutter may have one or more locking tabs associated with it. The corresponding disk drive includes a mechanism for opening the door or shutter on the cartridge as the cartridge is pushed into the system. Such a mechanism may comprise a door link that makes contact with a locking tab, thereby unlocking the shutter. As the cartridge is inserted further into the drive, the shutter is opened to partially expose the information recording medium contained therein. This permits a disk hub to be loaded onto a spindle of a motor or other drive mechanism, and permits entry of a read-write head and a bias magnetic into the protective cartridge. The disk, when rotated by the drive mechanism, permits the read-write head to access all portions of the disk media.
To conserve space in optical storage systems, it is desirable to minimize the size required by the apparatus that loads a disk onto and unloads the disk from a spindle. Conventional loading and unloading devices vary depending upon the type of disk being used. A conventional disk loading and unloading system that uses disk cartridges is typically capable of automatically transporting a disk cartridge from a receiving port onto the spindle. When the disk is no longer required, a conventional disk loading and unloading system automatically unloads the disk from the spindle. A loading device for performing this loading and unloading of the disk is generally constructed so that during disk loading (i.e., when the disk is moved from an ejected position into the player and onto the spindle), the disk is moved horizontally, parallel to the baseplate and turntable, towards the turntable. When the disk has been positioned above the turntable, the disk is lowered vertically, perpendicular to the face of the turntable, onto the spindle. Once on the turntable, a spindle magnet attracts the disk hub fixed to the center of the media, thereby clamping the disk in a rotatable condition for read-write operations.
When an operator is finished using the disk, the operator initiates an eject operation. The most common solution for ejecting a cartridge and disk from a spindle is the technique used in most Japanese drives. In this type of disk unloading apparatus, a cartridge "box" has four pins at its sides, and the pins ride in tracks in an adjacent sheet metal guide. During disk ejection, the cartridge box lifts the disk straight up and off the spindle. The apparatus then moves the disk horizontally, parallel to the baseplate and turntable, towards the disk receiving port in the front of the player. When the disk is thus lifted from the spindle during the unloading operation, it is necessary to generate sufficient upward force on the cartridge to overcome the magnetic clamping force holding the disk hub on the spindle magnet. The peak upward force required to overcome the magnetic clamping force may be produced by the manual operation of an ejection lever or by the activation of an electric ejection system.
In conventional electric ejection systems, wherein the disk cartridge unloading apparatus vertically lifts the disk cartridge to break the magnetic force between the spindle magnet and the disk hub, the electric ejection motor must generate a large load to effect removal of the disk cartridge. Consequently, when an operator opts to use the electric ejection system, a large motor having a large torque is required to generate sufficient vertical lifting force. Space must be reserved in the system housing to accommodate this large motor, thereby increasing the overall size of the housing for the cartridge-loading apparatus. In addition, the large motor consumes a considerable amount of power.
It is thus desirable to reduce the complexity of the disk player, while reducing the overall size of the player to facilitate the drive's convenient use in computer applications. In order to be able to receive a 51/4 inch disk cartridge and yet be small enough to be conveniently used in conjunction with a personal computer, optical disk drives must use compact and carefully located mechanical and electrical subsystems.
With this in mind, it is desirable to reduce the size of the required ejection motor. One way to effect this result is to reduce the amount of force required to break the magnetic clamping force holding the disk hub on the spindle magnet. By reducing this required force, it is possible to use a smaller ejection motor in the player. Hence, a disk loading apparatus design wherein the disk is not vertically lifted off of the spindle magnet, but is, rather, "peeled" from the magnet would be advantageous.
A conventional method that attempts to achieve this peeling action has the turntable and spindle swing down away from the disk. This method is discussed in U.S. Pat. No. 4,791,511 granted to Marvin Davis. It would nevertheless be of benefit to design a drive wherein the disk is peeled from the spindle magnet.